In the title compound, C(6)H(8)BNO(2)·H(2)O, the almost planar boronic acid mol-ecules (r.m.s. deviation = 0.044 Å) form inversion dimers, linked by pairs of O-H⋯O hydrogen bonds. The water mol-ecules link these dimers into [100] chains by way of O-H⋯O hydrogen bonds, and N-H⋯O links generate (100) sheets.